Re: [edk2-devel] [RFC PATCH] OvmfPkg/PlatformCI VS2019: Enable temporary workaround for cpuhp bugfix

["Ard Biesheuvel" <ardb@kernel.org>]

On Fri, 20 Jan 2023 at 10:25, Laszlo Ersek <lersek@redhat.com> wrote:
>
> On 1/19/23 14:43, Ard Biesheuvel wrote:
> > QEMU for x86 has a nasty CPU hotplug bug of which the ramifications are
> > difficult to oversee, even though KVM acceleration seems to be
> > unaffected. This has been addressed in QEMU mainline, and will percolate
> > through the ecosystem at its usual pace. In the mean time, due to the
> > potential impact on production workloads, we will be updating OVMF to
> > abort the boot when it detects a QEMU build that is affected.
> >
> > Tiancore's platform CI uses QEMU in TCG mode, and is therefore impacted
> > by this mitigation, unless its QEMU builds are updated. This has been
> > done for Ubuntu-GCC5, but Windows-VS2019 still uses a QEMU build that is
> > affected.
> >
> > Aborting the boot upon detecting the QEMU issue will render all boot
> > tests carried out on Windows-VS2019 broken unless we implement the
> > 'escape hatch' that enables proceed-at-your-own-risk mode, and permits
> > the boot to proceed even if the QEMU issue is detected.
> >
> > So let's enable this for Windows-VS2019, and remove it again once it is
> > no longer needed.
> >
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Cc: Gerd Hoffmann <kraxel@redhat.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > Cc: Michael Brown <mcb30@ipxe.org>
> > Cc: Oliver Steffen <osteffen@redhat.com>
> > Cc: Michael Kubacki <michael.kubacki@microsoft.com>
> >
> > Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml |  2 +-
> >  OvmfPkg/PlatformCI/PlatformBuildLib.py                | 12 ++++++++++++
> >  2 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml b/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
> > index 7e63f419b26b..b3b91aa84ea0 100644
> > --- a/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
> > +++ b/OvmfPkg/PlatformCI/.azurepipelines/Windows-VS2019.yml
> > @@ -24,7 +24,7 @@ jobs:
> >        package: 'OvmfPkg'
> >        vm_image: 'windows-2019'
> >        should_run: true
> > -      run_flags: "MAKE_STARTUP_NSH=TRUE QEMU_HEADLESS=TRUE"
> > +      run_flags: "MAKE_STARTUP_NSH=TRUE QEMU_HEADLESS=TRUE QEMU_CPUHP_QUIRK=TRUE"
> >
> >      #Use matrix to speed up the build process
> >      strategy:
> > diff --git a/OvmfPkg/PlatformCI/PlatformBuildLib.py b/OvmfPkg/PlatformCI/PlatformBuildLib.py
> > index bfef9849c749..58dc1189a2cc 100644
> > --- a/OvmfPkg/PlatformCI/PlatformBuildLib.py
> > +++ b/OvmfPkg/PlatformCI/PlatformBuildLib.py
> > @@ -170,6 +170,7 @@ class PlatformBuilder( UefiBuilder, BuildSettingsManager):
> >          self.env.SetValue("PRODUCT_NAME", "OVMF", "Platform Hardcoded")
> >          self.env.SetValue("MAKE_STARTUP_NSH", "FALSE", "Default to false")
> >          self.env.SetValue("QEMU_HEADLESS", "FALSE", "Default to false")
> > +        self.env.SetValue("QEMU_CPUHP_QUIRK", "FALSE", "Default to false")
> >          return 0
> >
> >      def PlatformPreBuild(self):
> > @@ -211,6 +212,17 @@ class PlatformBuilder( UefiBuilder, BuildSettingsManager):
> >              args += " -pflash " + os.path.join(OutputPath_FV, "OVMF.fd")    # path to firmware
> >
> >
> > +        ###
> > +        ### NOTE This is a temporary workaround to allow platform CI to cope with
> > +        ###      a QEMU bug in the CPU hotplug code. Once the CI environment has
> > +        ###      been updated to carry a fixed version of QEMU, this can be
> > +        ###      removed again
> > +        ###
> > +        ### Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
> > +        ###
> > +        if (self.env.GetValue("QEMU_CPUHP_QUIRK").upper() == "TRUE"):
> > +            args += "  -fw_cfg name=opt/org.tianocore/X-Cpuhp-Bugcheck-Override,string=yes"
> > +
> >          if (self.env.GetValue("MAKE_STARTUP_NSH").upper() == "TRUE"):
> >              f = open(os.path.join(VirtualDrive, "startup.nsh"), "w")
> >              f.write("BOOT SUCCESS !!! \n")
>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
>
> Technically speaking, can I merge this *prepended* to my v3 patch set
> ([PATCH v3 0/2] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg
> block regression), in the *same* PR?
>
> Because then I'll do that, saving us a bit of duplicated work.
>

Yes, please go ahead and merge this if it is all ready to go. I won't
get around to it to later this afternoon.

> I'll then also file the BZ for reverting this (once I know the commit
> hash), for when a new QEMU is out for Windows -- whom should I assign
> that BZ? Oliver or Ard?
>

You can assign it to me. And please put Michael Kubacki on cc as well.